This invention relates to fluorinated resins having a hydrophilic surface. More particularly, this invention relates to fluorinated resins that maintain a high hydrophilicity even at a prolonged exposure and have a high wettability as result of forming a thin film of hydrophilic substance on the surface with increased surface roughness.
Fluorinated resins are commonly known as polymers which are primarily comprised of elements including carbon and fluorine.
Generally, known fluorinated resins include polytetrafluoroethylene (PTFE), fluorinated ethylenepropylene(FEP) copolymer, perfluoroalkylvinyl ether(PFA) polymer, and polychlorotrifluoroethylene (PCTFE), and the like.
Fluorinated resins are characterized by inertness, thermal stability, hydrophobicity, a low coefficient of friction and low adhesion. While such properties are advantageous for fluorinated resins, they could also be disadvantageous when it comes to expanding the scope of applications for resins.
For example, various forms of fluorinated resins have been developed in the field that requires bio-compatibility, but because of their chemical inertness and extremely low reactivity, the development has been very limited.
In addition, while it is suitable for fluorinated resins having low surface energy in the field of permeable membranes or filters to be used for permeation of liquids with low surface tension, such is not suitable for selective permeation of liquids having high surface tension ( greater than 50dynes/cm).
Furthermore, PTFE has also been under intense study for its applications in the membrane of cell culture, but a low adherence between surfaces of PTFE having a low surface energy has been problematic.
Up until now, extensive studies for modifying the physical properties of the surface of the fluorinated resins by many investigations have been undertaken, but satisfactory results thereof have not yet been attained.
U.S. Pat. No. 4,548,867, for example, discloses fluorinated resin products having improved surface properties as evidenced by increased wettability, printability and adhesive property after the treatment of fluorinated resin with a low temperature plasma comprising an organic nitrogen-containing gas.
U.S. Pat. No. 4,946,903 discloses an invention which involves an increase in surface energy of fluorinated resins by means of RF (radio frequency) discharge in which surface""s fluorine is substituted with hydrogen or oxygen.
However, fluorinated resins prepared by the above-mentioned patents have not reached to a satisfactory level in terms of wettability.
It is therefore an object of the present invention to provide fluorinated resins having increased surface roughness with the formation of thin films of hydrophilic substance to obtain high wettability and maintain hydrophilicity even after prolonged exposure to atmosphere.
This invention provides fluorinated resins exhibiting high wettability by increasing the central line roughness average of the fluorinated resin surface to more than 0.1 xcexcm and forming a hydrophilic thin film on the surface having increased roughness while maintaining a central line roughness average of greater than 0.1 xcexcm.